Reduced Platelet Adhesion Research Articles

Bioinspired PLCL/Elastin Nanofibrous Vascular Tissue Engineering Scaffold Enhances Endothelial Cells and Inhibits Smooth Muscle Cells.

In vascular tissue engineering, a scaffold that can enhance the proliferation of endothelial cells (ECs) while inhibiting the synthetic differentiation of smooth muscle cells (SMCs) is crucial to prevent thrombus and restenosis after graft implantation. However, it is always challenging to incorporate both properties simultaneously in a vascular tissue engineering scaffold. In this study, a novel composite material was developed by combining a synthetic biopolymer of poly(l-lactide-co-caprolactone) (PLCL) and a natural biopolymer of elastin through electrospinning. Cross-linking of the PLCL/elastin composite fibers using EDC/NHS was performed to stabilize the elastin component. The incorporation of elastin into PLCL was found to enhance the hydrophilicity and biocompatibility of the resulting PLCL/elastin composite fibers, as well as the mechanical properties. Additionally, as a natural component of the extracellular matrix, elastin displayed antithrombotic properties reducing platelet adhesion and improving blood compatibility. Results of cell culture experiments with human umbilical vein ECs (HUVECs) and human umbilical artery SMCs (HUASMCs) showed that the composite fiber membrane had high cell viability, promoting the proliferation and adhesion of HUVECs and inducing a contractile phenotype in HUASMCs. These results indicate that the PLCL/elastin composite material has great potential for use in vascular graft applications due to its favorable properties and rapid endothelialization and contractile phenotypes of cells.

Preparation of biomolecules-mimic poly (ether sulfone)-based hydrogels and their anti-thrombotic, endothelialization and anti-microbial properties

The development of novel hydrogels with high biocompatibility is a vital and active topic of study. Here, we used a facile polycondensation approach to develop multifunctional poly (ether sulfone) (PES)-based hydrogels with diverse functional groups (−SO3Na, −COONa, −OH, and − NH2), as indicated by flourier transformed infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The chemical structure of the PES-based hydrogels could be modulated by monomer selection and post-treatment, resulting in a wide range of biomolecule-mimic structures and matching biological functions. In the current investigation, heparin-mimic PES-based hydrogels demonstrated good hemocompatibility, as evident by reduced platelet adhesion and activation, delayed clotting times, suppressed blood-related complement activations, and CD11b expression on leukocytes in the blood. Moreover, hyper-sulfonated PES-based hydrogels showed exceptional cytocompatibility with human umbilical vein endothelial cells (HUVECs) and considerable antiproliferative activity against human umbilical artery smooth muscle cells (HUASMCs), as revealed by cell proliferation and cytotoxicity assay findings. Finally, chitosan-mimic PES-based hydrogels had marked anti-microbial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), as shown by the number of colonies. The aforementioned bio-functions were attributed to the formation of various chemical structures on the surfaces of PES-based hydrogels. The distinctive PES-based hydrogels synthesized in this work would be of high utility not only in the synthesis of biomedical hydrogels but also in the rational design of various types of biocompatible materials.

A Commercial Nonbinding Surface Effectively Reduces Fibrinogen Adsorption but Does Not Prevent Platelet Adhesion to Fibrinogen.

A commercial nonbinding surface effectively prevents protein adsorption; however, the platelet phenotype on this surface has yet to be defined. This study evaluates platelet adhesion and adsorption of several plasma/extracellular matrix (ECM) proteins to the nonbinding surface compared to other commonly used nontreated and high-binding surfaces. Platelet adhesion to uncoated microplates and those coated with fibrinogen or collagen is quantified by colorimetric assay. The binding capacity of the examined surfaces for plasma/ECM proteins is evaluated by measuring the relative and absolute protein adsorption. Compared to other surfaces, the nonbinding surface effectively prevents platelet adsorption, i.e. by 61-93% (Enzyme-Linked Immunosorbent Assay, ELISA), and reduces platelet adhesion, i.e. by 92%, when not coated with any protein. The nonbinding surface also decreases platelet deposition on collagen (up to 31%), but not fibrinogen. The nonbinding surface seems to be more of a low-fouling than nonfouling material, as it is able to reduce fibrinogen adsorption but not prevent platelet adhesion to fibrinogen. This feature should be considered when using the nonbinding surface for in vitro platelet testing.

Cargo-free particles divert neutrophil-platelet aggregates to reduce thromboinflammation

The combination of inflammation and thrombosis is a hallmark of many cardiovascular diseases. Under such conditions, platelets are recruited to an area of inflammation by forming platelet-leukocyte aggregates via interaction of PSGL-1 on leukocytes and P-selectin on activated platelets, which can bind to the endothelium. While particulate drug carriers have been utilized to passively redirect leukocytes from areas of inflammation, the downstream impact of these carriers on platelet accumulation in thromboinflammatory conditions has yet to be studied. Here, we explore the ability of polymeric particles to divert platelets away from inflamed blood vessels both in vitro and in vivo. We find that untargeted and targeted micron-sized polymeric particles can successfully reduce platelet adhesion to an inflamed endothelial monolayer in vitro in blood flow systems and in vivo in a lipopolysaccharide-induced, systemic inflammation murine model. Our data represent initial work in developing cargo-free, anti-platelet therapeutics specifically for conditions of thromboinflammation.

Femtosecond Laser‐Induced Hydrophobic Surface of NiTi Shape Memory Alloy and its Blood Compatibility

The study of nickel–titanium shape memory alloy (NiTi SMA) surface wettability is important to improve the blood compatibility of medical implant materials. Herein, a femtosecond laser with a wavelength of 1030 nm is used to process the hydrophobic surface of NiTi SMA. A scanning electron microscope, an X‐ray photoelectron spectrometer, a surface profiler, and a contact angle meter are used to measure the microstructure, the chemical composition, the surface roughness, and the surface contact angle of NiTi SMA. The influence of the laser fluence on the NiTi SMA surface wettability is analyzed using the Wenzel–Cassie composite model. The results show that as the laser fluence increases, the surface roughness gradually increases and then fluctuates. Moreover, a rapid increase followed by a gradual rise is observed in the surface contact angle. The blood compatibility of NiTi SMA surface increases with the increase in the surface contact angle. Specifically, the superhydrophobic surface with high contact angle and low rolling angle can significantly improve hemolysis and coagulation while reducing platelet adhesion and deformation. The study of the superhydrophobic microstructure of NiTi SMA surface will provide a new approach for improving the blood compatibility of medical implant materials.

Modified poly (4-methyl-1-pentene) membranes by surface segregation for blood oxygenation

Oxygenation membranes in extracorporeal membrane oxygenation (ECMO) with excellent gas permeability, good hemocompatibility and durable resistance to plasma leakage is the key to achieve long-term and efficient blood oxygenation. This study put forward surface segregation strategy in thermally induced phase separation (TIPS) of poly (4-methyl-1-pentene) (PMP) membranes to realize the in-situ surface modification. Heterostructured PMP membranes with hydrophilic hemocompatible surface and hydrophobic body were obtained by migration of hydrophilic segments of the amphiphilic block copolymer Pluronic F127 to the surface in their preparation process. The hydrophilic surface could effectively improve hemocompatibility of membranes through hydration layer effect and steric hindrance effect, also reduce platelet adhesion significantly, and prolong the coagulation time of the four coagulation items within the normal physiological range of human body. When adding 10 wt% F127, the membrane exhibited an optimum CO2 permeance of ∼11461 GPU and O2 permeance of ∼13335 GPU, respectively, and an optimized blood oxygenation performance in vitro with O2 flux of 122.9 ml min−1 m−2 and CO2 flux of 129.2 ml min−1 m−2, and the asymmetric structure ensures resistance to plasma leakage for more than two months, that showed great application potential. Besides, preparation of hollow fiber membranes based on surface segregation was also explored, aiming to realize the enhanced performance and large-scale preparation of PMP oxygenation membranes. The membranes prepared in this work exhibited an outstanding performance when applied in blood oxygenation, showing great application potentials.

The anti-platelet activity of panaxadiol fraction and panaxatriol fraction of Korean Red Ginseng in vitro and ex vivo

BackgroundThe anti-platelet activity of the saponin fraction of Korean Red Ginseng has been widely studied. The saponin fraction consists of the panaxadiol fraction (PDF) and panaxatriol fraction (PTF); however, their anti-platelet activity is yet to be compared. Our study aimed to investigate the potency of anti-platelet activity of PDF and PTF and to elucidate how well they retain their anti-platelet activity via different administration routes. MethodsFor ex vivo studies, Sprague-Dawley rats were orally administered 250 mg/kg PDF and PTF for 7 consecutive days before blood collection via cardiac puncture. Platelet aggregation was conducted after isolation of the washed platelets. For in vitro studies, washed platelets were obtained from Sprague-Dawley rats. Collagen and adenosine diphosphate (ADP) were used to induce platelet aggregation. Collagen was used as an agonist for assaying adenosine triphosphate release, thromboxane B2, serotonin, cyclic adenosine monophosphate, and cyclic guanosine monophosphate (cGMP) release. ResultsWhen treated ex vivo, PDF not only inhibited ADP and collagen-induced platelet aggregation, but also upregulated cGMP levels and reduced platelet adhesion to fibronectin. Furthermore, it also inhibited Akt phosphorylation induced by collagen treatment. Panaxadiol fraction did not exert any anti-platelet activity in vitro, whereas PTF exhibited potent anti-platelet activity, inhibiting ADP, collagen, and thrombin-induced platelet aggregation, but significantly elevated levels of cGMP. ConclusionOur study showed that in vitro and ex vivo PDF and PTF treatments exhibited different potency levels, indicating possible metabolic conversions of ginsenosides, which altered the content of ginsenosides capable of preventing platelet aggregation.

Functionalization of 3D printed polymeric bioresorbable stents with a dual cell-adhesive peptidic platform combining RGDS and YIGSR sequences.

Biomimetic surface modification with cell-adhesive peptides is a promising approach to improve endothelialization of current bioresorbable stents (BRS). Among them, RGDS and YIGSR sequences have been reported to mediate adhesion and migration of endothelial cells (ECs) while preventing platelet activation. This work presents the functionalization of novel 3D-printed poly-L-lactic acid (PLLA) and poly(L-lactic-co-ε-caprolactone) (PLCL) BRS with linear RGDS and YIGSR sequences, as well as a dual platform (PF) containing both motifs within a single biomolecule. Functionalized surfaces were characterized in terms of static contact angle, biomolecule distribution under confocal fluorescence microscopy and peptide quantification via detachment from the surface, showing a biomolecule density in the range of 0.5 to 3.5 nmol cm-2. Biological evaluation comprised a cell adhesion test on functionalized films with ECs and a blood perfusion assay on functionalized stents to assess ECs response and device hemocompatibility, respectively. Cell adhesion assays evidenced significantly increased cell number and spreading onto functionalized films with respect to control samples. Regarding stents' hemocompatibility, platelet adhesion onto PLCL stents was severely decreased with respect to PLLA. In addition, functionalization with RGDS, YIGSR and the PF rendered BRS stents displaying even further reduced platelet adhesion. In conclusion, the combination of intrinsically less prothrombogenic materials such as PLCL and its functionalization with EC-discriminating adhesive biomolecules paves the way for a new generation of BRS based on accelerated re-endothelialization approaches.

Tannic Acid-Assisted Immobilization of Copper(II), Carboxybetaine, and Argatroban on Poly(ethylene terephthalate) Mats for Synergistic Improvement of Blood Compatibility and Endothelialization.

Due to thrombosis and intimal hyperplasia, small-diameter vascular grafts have poor long-term patency. A combination strategy based on nitric oxide (NO) and anticoagulants has the potential to address those issues. In this study, poly(ethylene terephthalate) (PET) mats were prepared by electrospinning and coated with tannic acid (TA)/copper ion complexes. The chelated copper ions endowed the mats with sustained NO generation by catalytic decomposition of endogenous S-nitrosothiol. Subsequently, zwitterionic carboxybetaine acrylate (CBA) and argatroban (AG) were immobilized on the mats. The introduced AG and CBA had synergistic effects on the improvement of blood compatibility, resulting in reduced platelet adhesion and prolonged blood clotting time. The biocomposite mats selectively promoted the proliferation and migration of human umbilical vein endothelial cells while inhibiting the proliferation and migration of human umbilical arterial smooth muscle cells under physiological conditions. In addition, the prepared mats exhibited antibacterial activity against Escherichia coli and Staphylococcus aureus. Collectively, the prepared mats hold great promise as artificial small-diameter vascular grafts.

Regulatory Effects of Curcumin on Platelets: An Update and Future Directions.

The rhizomatous plant turmeric, which is frequently used as a spice and coloring ingredient, yields curcumin, a bioactive compound. Curcumin inhibits platelet activation and aggregation and improves platelet count. Platelets dysfunction results in several disorders, including inflammation, atherothrombosis, and thromboembolism. Several studies have proved the beneficial role of curcumin on platelets and hence proved it is an important candidate for the treatment of the aforementioned diseases. Moreover, curcumin is also frequently employed as an anti-inflammatory agent in conventional medicine. In arthritic patients, it has been shown to reduce the generation of pro-inflammatory eicosanoids and to reduce edema, morning stiffness, and other symptoms. Curcumin taken orally also reduced rats' acute inflammation brought on by carrageenan. Curcumin has also been proven to prevent atherosclerosis and platelet aggregation, as well as to reduce angiogenesis in adipose tissue. In the cerebral microcirculation, curcumin significantly lowered platelet and leukocyte adhesion. It largely modulated the endothelium to reduce platelet adhesion. Additionally, P-selectin expression and mice survival after cecal ligation and puncture were improved by curcumin, which also altered platelet and leukocyte adhesion and blood-brain barrier dysfunction. Through regulating many processes involved in platelet aggregation, curcuminoids collectively demonstrated detectable antiplatelet activity. Curcuminoids may therefore be able to prevent disorders linked to platelet activation as possible therapeutic agents. This review article proposes to highlight and discuss the regulatory effects of curcumin on platelets.

Elevated Serum Amyloid A Levels Contribute to Increased Platelet Adhesion in COVID-19 Patients.

Coronavirus disease-19 (COVID-19) patients are prone to thrombotic complications that may increase morbidity and mortality. These complications are thought to be driven by endothelial activation and tissue damage promoted by the systemic hyperinflammation associated with COVID-19. However, the exact mechanisms contributing to these complications are still unknown. To identify additional mechanisms contributing to the aberrant clotting observed in COVID-19 patients, we analyzed platelets from COVID-19 patients compared to those from controls using mass spectrometry. We identified increased serum amyloid A (SAA) levels, an acute-phase protein, on COVID-19 patients' platelets. In addition, using an in vitro adhesion assay, we showed that healthy platelets adhered more strongly to wells coated with COVID-19 patient serum than to wells coated with control serum. Furthermore, inhibitors of integrin aIIbβ3 receptors, a mediator of platelet-SAA binding, reduced platelet adhesion to recombinant SAA and to wells coated with COVID-19 patient serum. Our results suggest that SAA may contribute to the increased platelet adhesion observed in serum from COVID-19 patients. Thus, reducing SAA levels by decreasing inflammation or inhibiting SAA platelet-binding activity might be a valid approach to abrogate COVID-19-associated thrombotic complications.

Polyphenol based hybrid nano-aggregates modified collagen fibers of biological valve leaflets to achieve enhanced mechanical, anticoagulation and anti-calcification properties

Glutaraldehyde (Glut)-crosslinked porcine pericardium and bovine pericardium are mainly consisted of collagen and widely used for the preparation of heterogenous bioprosthetic heart valves (BHV), which play an important role in the replacement therapy of severe valvular heart disease, while their durability is limited by degeneration due to calcification, thrombus, endothelialization difficulty and prosthetic valve endocarditis. Herein, we develop a novel BHV, namely, TPly-BP, based on natural tannic acid and polylysine to improve the durability of Glut crosslinked bovine pericardium (Glut-BP). Impressively, tannic acid and polylysine could form nanoaggregates via multiple hydrogen bonds and covalent bonds, and the introduction of nanoaggregates not only improved the mechanical properties and collagen stability but also endowed TPly-BP with good biocompatibility and hemocompatibility. Compared to Glut-BP, TPly-BP showed significantly reduced cytotoxicity, improved endothelial cell adhesion, a low hemolysis ratio and obviously reduced platelet adhesion. Importantly, TPly-BP exhibited great antibacterial and in vivo anti-calcification ability, which was expected to improve the in vivo durability of BHVs. These results suggested that TPly-BP would be a potential candidate for BHV.Graphical abstract

Construction of enzyme-laden vascular scaffolds based on hyaluronic acid oligosaccharides-modified collagen nanofibers for antithrombosis and in-situ endothelialization of tissue-engineered blood vessels

The current use of synthetic grafts often yields low patency in the reconstruction of small-diameter blood vessels owing to the deposition of thrombi and imperfect coverage of the endothelium on the graft lumen. Therefore, the design of vascular scaffolds with antithrombotic performance and endothelialization is greatly required. Herein, we developed an enzyme-laden scaffold based on hyaluronic acid oligosaccharides-modified collagen nanofibers (labeled HA-COL) to improve the anti-platelet capacity and endothelialization of vascular grafts. In this study, HA-COL nanofibers not only encouraged the endothelialization of vascular scaffolds, but acted as an antiplatelet enzyme-laden platform. Apyrase (Apy) and 5’-nucleotidase (5’-NT) were covalently grafted onto the nanofibers, which in turn converted the platelet-sensitive substance: adenosine diphosphate (ADP) into adenosine monophosphate (AMP) and adenosine, thereby, improving the antithrombotic performance of the scaffolds. Notably, the catalytic end-product: adenosine would work in coordination with HA-COL to synergistically enhance the endothelialization of the vascular scaffolds. The results demonstrated that the enzyme-laden scaffolds maintained catalytic performance, reduced platelet adhesion and aggregation, and guaranteed higher patency after 1-month in situ transplantation. Moreover, these scaffolds showed optimal cytocompatibility, tissue compatibility, scaffold biodegradability and tissue regenerative capability during in vivo implantation. Overall, these engineered vascular scaffolds demonstrated their capacity for endothelialization and antithrombotic performance, suggesting their potential for small-diameter vascular tissue engineering applications. Statement of significanceConsidering the critical problems in small-diameter vascular reconstruction, the enzyme-laden vascular scaffolds were prepared for improving in-situ endothelialization and antithrombotic performances of artificial blood vessels. The electrospun HA-COL nanofibers were used as the main matrix materials, which provided favorable structural templates for the regeneration of vasculature and functioned as a platform for the loading of enzymes. The enzyme-laden scaffolds with the biomimetic cascading reaction would convert ADP into adenosine, thereby, decreasing the sensitivity of platelets and improving the antithrombotic performance of tissue-engineered blood vessels (TEBVs). The nanofibrous scaffolds exhibited optimal cytocompatibility, tissue compatibility and regenerative capability, working together with catalytic products of dual-enzyme reaction that would synergistically contribute to TEBVs endothelialization. This study provides a new method for the improvement of in-situ endothelialization of small-diameter TEBVs while qualified with antithrombotic performance.

A study on in-vitro behaviour of stainless steel 316L subjected to rotational magnetorheological abrasive flow finishing process

In Rotational Magnetorheological Abrasive Flow Finishing (R-MRAFF) process, Magnetic Field Intensity (MFI) is the primary factor for the formation of ferrous chains which is responsible for finishing. Changing the pole distance between magnets to achieve a difference in MFI values will alter the strength of the ferrous chains. In this study, three different MFI values such as 0.34, 0.36, and 0.40 Tesla were chosen for finishing on Stainless Steel 316L (SS 316L). Surface wettability, bio-corrosion, and hemocompatibility studies were conducted to investigate the in-vitro behavior of SS 316L. The wettability of the implants changed from hydrophobic (100.92°) to hydrophilic (83.452°) surface as the MFI value increased. Bio-corrosion studies revealed improved corrosion resistance for R-MRAFF process finished samples, with the corrosion rate reduced from 3.693 to 0.967 μm year−1. Hemocompatibility of SS 316L was improved with reduced platelet adhesion when compared to the pristine sample.

The loading of C-type natriuretic peptides improved hemocompatibility and vascular regeneration of electrospun poly(ε-caprolactone) grafts

As a result of thrombosis or intimal hyperplasia, synthetic artificial vascular grafts had a low success rate when they were used to replace small-diameter arteries (inner diameter < 6 mm). C-type natriuretic peptides (CNP) have anti-thrombotic effects, and can promote endothelial cell (EC) proliferation and inhibit vascular smooth muscle cell (SMC) over-growth. In this study, poly(ε-caprolactone) (PCL) vascular grafts loaded with CNP (PCL-CNP) were constructed by electrospinning. The PCL-CNP grafts were able to continuously release CNP at least 25 days in vitro. The results of scanning electron microscopy (SEM) and mechanical testing showed that the loading of CNP did not change the microstructure and mechanical properties of the PCL grafts. In vitro blood compatibility analysis displayed that PCL-CNP grafts could inhibit thrombin activity and reduce platelet adhesion and activation. In vitro cell experiments demonstrated that PCL-CNP grafts activated ERK1/2 and Akt signaling in human umbilical vein endothelial cells (HUVECs), as well as increased cyclin D1 expression, enhanced proliferation and migration, and increased vascular endothelial growth factor (VEGF) secretion and nitric oxide (NO) production. The rabbit arteriovenous (AV)-shunt ex vitro indicated that CNP loading significantly improved the antithrombogenicity of PCL grafts. The assessment of vascular grafts in rat abdominal aorta implantation model displayed that PCL-CNP grafts promoted the regeneration of ECs and contractile SMCs, modulated macrophage polarization toward M2 phenotype, and enhanced extracellular matrix remodeling. These findings confirmed for the first time that loading CNP is an effective approach to improve the hemocompatibility and vascular regeneration of synthetic vascular grafts. Statement of significanceSmall-diameter (< 6 mm) vascular grafts (SDVGs) have not been made clinically available due to their prevalence of thrombosis, limited endothelial regeneration and intimal hyperplasia. The incorporation of bioactive molecules into SDVGs serves as an effective solution to improve hemocompatibility and endothelialization. In this study, for the first time, we loaded C-type natriuretic peptides (CNP) into PCL grafts by electrospunning and confirmed the effectiveness of loading CNP on improving the hemocompatibility and vascular regeneration of artificial vascular grafts. Regenerative advantages included enhancement of endothelialization, modulation of macrophage polarization toward M2 phenotypes, and improved contractile smooth muscle cell regeneration. Our investigation brings attention to CNP as a valuable bioactive molecule for modifying cardiovascular biomaterial.

Platelet dysfunction after trauma: From mechanisms to targeted treatment.

Platelet dysfunction after trauma: From mechanisms to targeted treatment.

Safety and Clinical Effectiveness of Pipeline Shield Device for Intracranial Aneurysms in an Australian Cohort (SCOPE‐AUS)

Background The Pipeline Flex Embolization Device (PED) with Shield Technology (PED‐Shield) is a third‐generation flow diverting stents with surface modification designed to reduce platelet adhesion and thrombogenicity. We report the long‐term safety and effectiveness of the PED‐Shield in the treatment of unruptured intracranial aneurysms in an Australian cohort. Methods SCOPE‐AUS (Safety and Clinical Effectiveness Of Pipeline Shield Embolization Device for Treatment of Intracranial Aneurysms in Australia) is a multicenter, single‐arm, retrospective study of patients with unruptured intracranial aneurysms treated with the PED‐Shield flow diverting stents at 3 high‐volume neurointervention centers in Australia between May 1, 2015, and June 30, 2018, evaluating safety and efficacy. The primary outcome was neurologic adverse event or neurologic‐related death at 1 year, and the secondary outcome was long‐term complete aneurysm occlusion. Results A total of 238 patients (mean age 55.8±11.0 years, 73.1% [174/238] female) and 278 aneurysms were treated via 247 procedures. Two (0.7%) aneurysms were retreated during the 18‐month follow‐up. Overall occlusion rates at 18 months or at last follow‐up imaging were 92.5% (233/252). There were 35 (14.7%) total primary end point events. The 12‐month neurologic morbidity and mortality rates were 3.8% (9/238) and 1.3% (3/238), respectively. For the subgroup of internal carotid artery aneurysms, mortality (0.7%) and morbidity (2.0%) rates were low, and the complete occlusion rate was 92.5% (147/155). Conclusions In this multicenter study, which includes a wide variety of both distal bifurcation and proximal unruptured intracranial aneurysms, the occlusion rates and safety outcomes of the PED‐Shield flow diverting stent demonstrate a high proportion of complete aneurysm occlusion, extremely low retreatment rates, and low complication rates.

Surface Modification of Polytetrafluoroethylene and Polycaprolactone Promoting Cell-Selective Adhesion and Growth of Valvular Interstitial Cells.

Tissue engineering concepts, which are concerned with the attachment and growth of specific cell types, frequently employ immobilized ligands that interact preferentially with cell types of interest. Creating multicellular grafts such as heart valves calls for scaffolds with spatial control over the different cells involved. Cardiac heart valves are mainly constituted out of two cell types, endothelial cells and valvular interstitial cells. To have control over where which cell type can be attracted would enable targeted cell settlement and growth contributing to the first step of an engineered construct. For endothelial cells, constituting the outer lining of the valve tissue, several specific peptide ligands have been described. Valvular interstitial cells, representing the bulk of the leaflet, have not been investigated in this regard. Two receptors, the integrin α9β1 and CD44, are known to be highly expressed on valvular interstitial cells. Here, we demonstrate that by covalently grafting the corresponding peptide and polysaccharide ligand onto an erodible, polycaprolactone (PCL), and a non-degradable, polytetrafluoroethylene (PTFE), polymer, surfaces were generated that strongly support valvular interstitial cell colonization with minimal endothelial cell and reduced platelet adhesion. The technology for covalent binding of corresponding ligands is a key element towards tissue engineered cardiac valves for in vitro applications, but also towards future in vivo application, especially in combination with degradable scaffold material.

A nitric oxide-donor pravastatin hybrid drug exerts antiplatelet and antiatherogenic activity in mice

Aim of the present study was to compare the lipid-lowering, antithrombotic and antiatherogenic properties of NCX-6550, nitropravastatin, a nitric-oxide donating derivative of pravastatin, with those of pravastatin in hypercholesterolemic mice. LDL receptor-deficient mice (LDLR–/–) on a normal diet (ND) showed enhanced cholesterol levels as compared to wild type (WT) mice (6.8±1.2 mmol/L and 2.8±0.82 mmol/L, respectively). High fat diet (HFD) induced a large enhancement of cholesterolemia in LDLR–/– mice (23.7±5.7 mmol/L, p&lt;0.0001 vs LDLR–/– ND and WT mice. Treatment with NCX 6550 (48 mg/kg), but not with equimolar pravastatin, reduced cholesterol in LDLR–/–HFD. Platelet adhesion to collagen under high shear rate (3000 sec–1) was significantly higher in LDLR–/– than in normal mice, and further enhanced in LDLR–/–HFD (-27%, p&lt;0.0001 vs untreated). NCX 6550 (48 mg/kg), but not pravastatin, reduced platelet adhesion, especially in LDLR–/–HFD. U46619-induced platelet aggregation ex vivo was also inhibited by NCX 6550 (48 mg/kg) but not by the parent compound. Finally, photochemically-induced acute (1 hr) femoral artery thrombosis and delayed (21 days) intimal thickening was assessed. Thrombus size was larger in LDLR–/– on HFD than in normocholesterolemic mice (0.46±0.04 vs 0.18±0.08 mg) and it was reduced by NCX 6550 (48 mg/kg) (0.08±0.02 mg, p&lt;0.0001), but not by pravastatin (0.4±0.01 mg p=NS). Intimal thickening was greater in hypercholesterolemic than in normal mice (I/M normal=0.53±0.16, LDLR–/–=1.1±0.15, LDLR–/–HFD=1.75 ±0.25). Both NCX 6550 and pravastatin reduced intimal thickening in normal (-95% and -74.5%, respectively) and LDLR–/– mice (-98% and -91%), while in strongly hyperlipidemic animals (LDLR–/–HFD) NCX 6550 was more effective than pravastatin (-98% vs -65%, p&lt;0.0001). NCX 6550 shows greater antithrombotic and antiatherogenic activity than pravastatin in highly hypercholesterolemic mice.

A PEGylation method of fabricating bioprosthetic heart valves based on glutaraldehyde and 2-amino-4-pentenoic acid co-crosslinking with improved antithrombogenicity and cytocompatibility

With the development of diagnostic techniques, the incidence of bioprosthetic heart valve thrombosis (BHVT) is found to be seriously underestimated. Developing bioprosthetic heart valves (BHVs) that have good hemocompatibility without sacrificing other properties such as hydrodynamics and durability will be an effective strategy to alleviate BHVT. In this study, we developed a PEGylation method by co-crosslinking and subsequent radical polymerization. 2-amino-4-pentenoic acid was used to introduce carbon-carbon double bonds for glutaraldehyde crosslinked pericardia. Then poly (ethylene glycol) diacrylate (PEGDA) was immobilized on pericardia by radical polymerization. A comprehensive evaluation of the modified pericardia was performed including structural characterization, hemocompatibility, cytocompatibility, mechanical properties, component stability, hydrodynamic performance and durability of the BHVs. The modified pericardia significantly reduced platelet adhesion by more than 75% compared with traditional glutaraldehyde crosslinked pericardia. Cell viability in the modified pericardia group was nearly 5-fold higher than that in glutaraldehyde crosslinked pericardia. The hydrodynamic performance met the requirements of ISO 5840–3 under physiological aortic valve conditions and its durability was proved after 200 million cycles of accelerated fatigue test. In conclusion, PEGDA modified pericardia exhibited improved antithrombogenicity and cytocompatibility properties compared with glutaraldehyde crosslinked pericardia. Statement of significanceBioprosthetic valve (BHV) implantation requires BHV to be structurally stable as well as biocompatible in vivo. Traditional glutaraldehyde crosslinking method prepared BHV suffers from severe cytotoxicity, thrombosis, and calcification. BHV modification methods that have simultaneously improved structural stability and biocompatibility were rarely reported. Here, we proposed a PEGylation method for BHV based on co-crosslinking strategy that could improve its structural stability as well as hemocompatibility. We take the advantage of high efficiency of glutaraldehyde crosslinking and demonstrate the feasibility and superiority of the PEGylated strategy, offering a promising option in glutaraldehyde-based BHV fabrication in the future.